For the "make something big" assignment, I'm designing and CNC milling the wood boxes for my Smart Beehive final project. I'm building a 10-frame Langstroth hive, which is the most common hive design used in beekeeping. The boxes are typically made from wood panels joined at the corners, which makes them a great fit for CNC machining.
Hive Dimensions
The standard 10-frame Langstroth dimensions I'm working with:
- Deep Hive Body: 9⅝" tall × 16¼" wide × 19⅞" long
- Medium Super: 6⅝" tall × 16¼" wide × 19⅞" long
The width and length stay the same between the deep body and the supers — only the height changes. The deep body is used for the brood chamber where the queen lays eggs, while the shorter supers stack on top for honey storage.
The Box Joint Problem on CNC
Box joints (also called finger joints) are the traditional way to join the corners of a wooden box — interlocking rectangular tabs that create a strong, clean joint with lots of glue surface area. They're the obvious choice for beehive boxes. The problem is that CNC routers use a round spinning bit, which means every internal corner comes out with a radius instead of a sharp 90° angle. You physically cannot cut a perfectly square inside corner with a round tool.
This is a fundamental limitation of CNC routing. When the bit cuts into an inside corner, it leaves a fillet with a radius equal to the bit's radius. So if you're using a 1/4" end mill, every inside corner will have a 1/8" radius. For box joints, this means the tabs won't seat flush into the slots — the rounded corners of the slot prevent the square corners of the tab from fully inserting.
There are a few common workarounds:
- Dog bone corners: Add small circular relief cuts at each inside corner so the mating piece can slide in past the radius. The circles extend just beyond the corner to clear the fillet.
- T-bone corners: Similar idea but the relief cut extends along one edge instead of diagonally, making it less visible on the finished joint.
- Chisel the corners by hand: After CNC cutting, go back and square up each inside corner with a chisel. More work but gives the cleanest result.
- Round the tabs to match: Instead of squaring the slots, round the edges of the tabs so they match the radius left by the bit.
After researching the different joint options, I decided to go with a full blind box joint. This type of joint hides the interlocking fingers from both sides of the corner, giving a clean exterior appearance while still providing the structural strength of a traditional box joint. Here's a great video that explains the different CNC joint types and shows how they look in practice:
Content coming soon — CAD design, toolpath setup, and cut files will be documented here.